Sherlock takes matters into his own hands when a killer with ties to his past terrorizes New York.

With a title like "M," Sherlock Holmes fans might have presumed this would be the episode in which we meet Holmes’ famed arch nemesis, Professor Moriarty. And it was, kinda. Though we’ve yet to lay eyes on Moriarty, we did learn his role in this iteration of the Sherlock Holmes’ universe. He's the man who murdered Sherlock’s love, Irene Adler.

In "M," a dark, intense episode that felt more like a big screen thriller than an hour of television, we saw Sherlock (Jonny Lee Miller) become unraveled for the first time as he readied himself to finally avenge his lover’s murder when "M," the killer he held responsible, struck close to home. Of course, the inevitable showdown between Sherlock and Moriarty can’t happen just yet and so we learn that it was Moriarty, not "M," who killed Irene as an unhinged Sherlock prepared to torture Moriarty’s football obsessed hired thug, (played by British actor, former football star himself and mutant villain, "Juggernaut," Vinnie Jones).

Sherlock’s questionable mental state finally pushed Watson (Lucy Liu), who continues to insist she has no interest in being an investigator despite regularly inserting herself into cases, to stay on. The kicker is she’s presumably doing it for free as Sherlock’s father turned down her offer to continue working with his son. All of this suggests it’s her feelings for Sherlock, rather than what he does, that makes Watson stay.

There’s nothing wrong with that and in fact, it’s become more and more apparent that Watson and Sherlock care for each other in their own roundabout, semi-insulting, non-romantic ways. What is frustrating is Watson’s stubborn refusal to admit she likes investigative work, or is at least good at it.

And while we’re on the topic of obstinance, we knew after Watson turned down his apprenticeship/housekeep offer that Sherlock would childishly try to distance himself from her by doing things like calling Watson "a crutch" and shooing her away from his investigations. Now that they she’s decided to stay, will there be a shift in the dynamic between these two? Hopefully, not too much.

With "M" now in custody and just as eager as Sherlock to take down Moriarty after his boss sold him out, "Elementary" is suddenly more than just a police procedural with the "Sherlock Holmes" brand grafted on to it. Sherlock and Watson finally have a larger purpose. Sherlock’s being to torture and kill Moriarty and Watson’s being to stop him. This is where "Elementary’s" version of Watson as Sherlock’s sober companion and caretaker becomes much more interesting and relevant.

In this world, Watson’s purpose is to keep Sherlock in check ethically, as well, as we saw when she reprimanded him for enlisting a thieving teenager in his plot to find "M." And by the end of the hour, it felt like Watson’s long-term role was finally established allowing "Elementary" to move on to bigger and better things, like the introduction of Moriarty.

Another nagging mystery was also to put to bed in "M," that being how Sherlock became an addict to begin with. Sherlock admitted to being a casual drug user in the past, but it was Irene’s brutal murder that sent him into a binge spiral and understandably so.

A pivotal episode that accomplished quite a bit in one hour, "M" is hopefully a sign of things to come on "Elementary." The initially odd pairing of Jonny Lee Miller and Lucy Liu turned out way better than expected and now we have the introduction of the larger "Sherlock Holmes" mythology in this episode. "Elementary" might not be the best version of "Sherlock Holmes," but it’s certainly proving to be one of the best new shows of the season.